Signaling system for railways



L. 'W. CHUBB.

SIGNALING SYSTEM FOR RAILWAYS.

APPLICATION man Nov .s.'1915.

J,,3 3,606. Patented Mar.16,1920.,

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UNITED STATES PATENT onnron- LEWIS W. CHU'BB, 0F EDG-EWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPQRATION OF PENNSYLVANIA.

SIGNALING sYsrnivi FOR RAILWAYS.

Specification of Letters Patent.

Application filed November 6, 1915. Serial No. 59,995.

citizen of the United States, and a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Signaling Systems for Railways, of which the following is a specification.

My invention relates to electrical systems of distribution and particularly to means whereby the two sides of an electrical circuit on which a plurality of alternating-current impulses of different frequencies are impressed, may be maintained at equal potentials as regards alternating current impulses having predetermined frequencies, while, simultaneously therewith, the sides of the same circuit may be maintained at different potentials as re gards alternating current impulses of other frequencles.

More particularly, my lnvention 18 adapted for use, in electrical-railway installations in which electrical signaling sys tems of the usual character are incorporated, the latter being operated by alternating currents having frequencies difierent from those of the propulsion currents.

In electrical-railway systems comprising a plurality of adjacent tracks, each of which is equipped with electrical signaling devices, unbalanced induced electromoti-ve forces may be impressed upon one of the track circuits by reason of the flow of propulsion currents in another of the tracks in close proximity thereto or in a neighboring feeder or trolley wire, Since one of the rails of the disturbed track is closer to the,

track in which the propulsion currents are flowing, the electromotive forces induced the other rail of the track which is more remote from the disturbing track. As a consequence, the electrical signaling devices associated with the trackon which the unequal induced electromotive forces are impressed, may be frequently influenced to indicate traflic conditions other than those that actually obtain. To overcome this difliculty, it is apparent'that means must be provided whereby the two rails of a track may be maintained at different potentials, as regards alternating currents having the frequency of the signaling currents only, but which, at the same time, are maintained at the same potential, as regardscurrents having other frequencies, such as the aforementioned induced currents. Of course, it will be understood that, under certain conditions, the terminals of the sig* naling relays may be maintained at the same .potential as regards alternating currents of a predetermined frequency or frequencies only.

An object of my invention is to provide means in an electrical system, whereby the potential difference between the two sides comprising the circuit is zero or substantially negligible, as regards currents of certain predetermined frequencies, while, at the same time, a potential diflerenceof any value may be maintained therebetween, as to currents of other frequencies.

For a better understanding of the nature and scope of my invention, reference may be had to the following description and to the accompanying drawing in which Figure 1 is a diagrammatic representation of an electrical-railway system embodying a form of my invention; Fig. 2 is a diagrammatic view of a modified form of the system shown in Fig. l, and Fig. 3 is a diagrammatic view showing, in detaihthe structure employed for accomplishing the above-mentioned results.

Referring to Fig. 1, I have shown for the purpose of illustration, two track'circuits 1 and 2 each having a separate trolley conductor3 which is electrically connected to one terminal of a source of power supply, shown as-a single-phase alternator/l. The other terminal of the alternator a is connected to the rails comprising the track circuits 1 and 2. Each track circuit comprises a track or block section 5, insulating joints 6 being inserted in the rails of each track in order to provide for the block sections employed in the signaling system. .Impedance bonds 7 ofthe usual character are connected on both sides of the insulating joints 6 in order that the propulsion currents may flow substantially unimpeded through the successive insulatedtrack sections. 'At the same time, the impedance bonds are so an ranged that they impede the flow therethrough of alternating current-s in a single Patented Mar.16,1920. V

. my invention.

direction only. It is usual to supply the signaling system with currents of higher frequencies than the propulsion currents -and,

consequently, the inductance of theimpedance bonds 7 constitutes a high impedance to the flow of the signaling currents.

For simplicity, I have shown the signaling system supplied for the track circuit only, but it will be understood that the signaling system may be applied to the track circuit 1 without affecting the operation of The signaling system comprises a source of current supply, shown as a single-phase alternator 8, the two terminals of which are connected to leads 9 which parallel the track 2' throughout those regions equipped with the signaling devices. At one end ofthe block 5, a transformer lOis inserted, a secondary winding 11 of which is connected across rails 12 and 13 of the track section 5. At the other end of the track sec tion 5 is placed a signaling device 14 which may be of any of the usual types. The naling device 14 is operated by a relay represented diagrammatically at 15, the two windings 16 and 17 of the relay being connected, respectively, in shunt to the track section 5 and in series with a secondary winding 18 of a track transformer 19. Since an alternating current, called the signaling current, is impressed upon the track section 5 by the transformer 10, the signaling current will normally flow through the winding 16 of the relay 15. At the same time, the winding 17 of the relay is traversed by a signaling current impressed by the transformer 19. A phase difference between the currents traversing the windings 16 and 17 is effected by means of an adjustable inductance element 20 which is connected in series circuit with the winding 16. The torque arising from the simultaneous flow of the displaced currents through the windings 16 and 17 effects rotation of an element 21 of the relay 15 whereby an arm 22, secured to the element 21, closes a circuit through the relay of the signaling device 14, thereby permitting the signaling device 14 to indicate that the block section 5 is open to traflic. The condition under which the signaling device 14 indicates a closed block section or danger, should be when a train bridges the rails 12 and 13 only.

Under this circumstance, the signaling our rents are shunted from the winding 16 of the relay 15, which, in turn, opens the circuit through the relay controlling the device 14, such as is well known in the art.

Assume, for instance, that a train is traversing the track circuit 1. As a result, the propulsion currents flowing simultaneously over the rails of the track circuit 1 induce disturbing eleetromotive forces in the rails 12 and 13 of the track circuit 2. The rail 12 being closer to the track circuit 1, has a higher electromotive force induced therein than the rail 13 and, consequently,

a potential difference may exist between the rails 12 and 13 at the points where conductors 27 and 28 are attached, which potentials may be sufficient to effect a current flow through the winding 16 of the relay 15 if, at the same time, a train bridges the rails 12 and 13 at some remote part of the block section 5. Since signaling relays, such as the relay 15, cannot be economically designed to operate at a certain definite frequency only, the relay 15, because of the current flow occasioned by the difference of potential between the rails 12 and 13, may indicate an open block when, in reality, a train is trav ersing the block 5 of the rail circuit 2.

It is necessary, therefore, to provide means whereby the rails 12 and 13 may be maintained at the same potential at the points of attachment of the relay 15 to the track circuit as regards the currents induced therein by reason of the flow of propulsion currents in the track circuit 1. To this end, I provide an auxiliary circuit 24 comprising an inductive reactance element 25 and a c011- densive reactance element 26, the same being connected in series relationship and their electrical constants being so adjusted that they constitute a resonant circuit for voltages of the frequency of the induced currents. Since the auxiliary circuit 24 is selective for currents of certain definite frequencies only, the signaling currents will not be shunted and will be forced to flow through the winding 16 of the relay 15. It will be apparent that any number of auxiliary circuits, similar to the auxiliary circuit 24, but severally tuned to various definite frequencies,

may be connected to corresponding points on the rails 12 and 13 and adjacent to the signaling relays in order to maintain the potentials of the rails at the critical points the same as regards currents of predetermined frequencies. At the same time, the potentials of the rails 12 and 13, as regards the signaling currents, will be maintained unimpaired. In actual practice, I have found that, by connecting the auxiliary circuit 24 in shunt to the relay winding 16, as represented at 24 the impedance drop of leads 27 and 28, permits the use of a resonant cir cuit of less current-carrying capacity. This is not essential, however, and is, in all respects, equivalent to connecting the circuit 24 in shunt to the rails 12 and 13, as hereinbefore explained.

In Fig. 2, I have employed auxiliary circuits acting-as shunts 24 whereby the di1"' ference in potential between the rails 12 and 13 may be compensated, as regards potentials arising from currents ha'vingrthe frequency of the propulsion currents flowing in the track circuit 1. As previously mentioned, I prefer to connect the auxiliary circuit 24 as shown at '2 in order that I may take advantage of the impedance oftheleads 27 and 28. In series with the winding 16 of the relay 15, I have connected an inductance ele ment 29 and a condensive element 30, the

electrical constants thereof being so adjusted that the circuit comprising the Winding 16 is a resonant circuit for alternating currents having the frequency of the signaling current only. 'Ihis additional ad]ustment acts circuit relationship with the relay winding 17. In this modified form, the relay 15 is precluded from being operated by any currents except those having, the frequency of in signaling current and, therefore, the signaling device lat will, in all cases, indicate the actual traiiic conditions obtaining upon the block 5. v 1

Since condensers of large capacity are expensive to construct and diflicult to make adjustable, a transformer, as shown in Fig. 3, has been substituted for the series-connected --inductive reactanceelement 25 and the condensive reactance element 26 comprising the auxiliary circuit 2%. 'The transformer of Fig. 3is, in all respects, the electrical equivalent of the auxillary circult 24 and comprises amain core member 31 which constitutes a closed magnetic circuit "for a primary members 35 and 36,'the internal reactance windin 32 havin a relativel small number of turns and a secondary winding 33 having a relatively large number of. turns. The primary winding 32 is adapted to be connected directly across the rails 12and 13, and the secondary winding 33' is connected in a closed circuit with a condensive element 3% having a constant capacity. Magneti- 7 cable inembers35 and 36 are disposed eX- teriorly of the core member 31 to bridge those legs ofthe core member 3I which are surrounded-by the primarywinding 32 and the secondary winding 38, respectively; 'By adjusting the air gaps 37 between the pole extensions 38 of the magnetizable shunt of the transformer may be varied so! that resonantconditions may obtain 1n the circurt comprising the primary winding 32 for those currents having a predetermined frequency.

The transformer of Fig.3 is fully disclosed in a co-pending patent application Serial No. 61,087, liledNove1nber. 12, 1915, by Charles LeGr. Fortescue, and assigned to the Westinghouse Electric &' Manufacturing Company.

' While I have shown and described several embodiments of my invention, it will be apparent to those skilled in the art that many nodifioations may be made therein without departing from the spirit-and scope of the appended claims.

I claim as my invention 1. In an electrical system, the combination with a circuit having a pair of circuit conductors which are maintained at a potential difference from each-other as re fgards alternating currents of a certain fre quency, of resonant circuits tuned for other frequencies and connected in shunt to said'circuit' conductors in order to"compensate for the potential difference therebetween when subjected to the flow of alternaing currents having frequencies corresponding to said tuned circuits. v

2. In an electrical system, the combina tion with a closed circuit comprising two conductors which are maintained at a pee tential'difference from each other asregards [alternating currents of a certain frequency,

of resonant means: for maintaining said two conductors at the .same potential as re gards alternating currents of certain other frequencies. c

In an electrical system, the combination with a closed circuit having two conductors whlch are mainta ned at different potentials to constitute a circuit'for the flow of alternating currents of a certain he quency, of resonantmeanswhereby said two'- conductors are simultaneously maintained at the same potential asregards alternating currents of other frequencies. V

4:. In a railway system, the combination with a track circuit having two rails that constitute a signaling circuit, one of said rails being the outgoing lead for the signaling current, and the other rail being the return lead for the signaling'current, of sei lies-connected inductive and condensive tained'at different potentials for currents having the frequency of, the sig'iialingrcur rent even though unequalpotentials of-other frequencies are induced I therein.

5. In a railway system, the combination with a track circuit having two rails that constitute the two sides of a signalingcin cuit, of series-connected inductive and condensive means whereby the two rails may be maintained at the same potential' for currentsof frequencies which 'Inay be induced therein and at different potentials for currents having the frequency of the signaling current.

56, In an electrical railway system, the combination with a plurality 'ofinsulatecl track sections constituting blocks for the electrical signaling system, and impedance bonds connecting'the track sections to one another whereby the propulsion currents may flow unimpeded through successive A block sections, of means whereby the rails of means whereby said two rails may be main combination with a plurality of insulated each track section are maintained at the same potential for alternating currents of frequencies which may be induced therein and at different potentials for currents having the frequency of the signaling currents.

7. In an electrical railway system, the

track sections constituting blocks for the electrical signaling system, and impedance bonds connecting the tracksections to one another whereby the. propulsion currents may flow unimpeded through successive block sections, of auxiliary circuits connected in shunt to the rails of each track'section whereby said rails at certain corresponding points may be'maintained at the same potential for an alternating current of a selected frequency but maintained at difi'er-.

ent potentials for currents having the frequency of the signaling current.

8. In an electrical railway system, the combinatlon with a plurality of insulated track sections constituting blocks for the electrical signaling system, and impedance bonds connecting the track sections to one another whereby the propulsion currents may flow unimpeded through successive block sections, of auxiliary circuits connected in shunt relation to the rails of each track section, said auxiliary circuits comprising condensive and inductive reactances which are so related as to provide a resonant circuit for an alternating current ofa selected V the terminals of said device is negligible for a current not of said selected frequency, and addit onal means connected in series with said device whereby. all currents excepting those of said selected frequency are precluded from flowing therethrough.

10. In an electrical system of distribution subject to the flow of alternating currents of different frequencies, the combination with an electrical device to be operated by an alternating current of a'selected frequency, of a resonant circuit connected in shunt thereto to maintain the potential difference 7 ductors and operated by currents of a select ed frequency, a circuit connected in shunt to said device and adapted .to carry a current having a frequency other than the selectedfrequency, and a second circuit connected in series with said device and adapted to carry a current of said selected frequency only.

12. In an electrical system comprising electrical conductors for the fiow of alternating currents of different frequencies, the combination with an electrical device that is connected to said conductors and is operated by an alternating current having a selected frequency, of a resonant circuit connected in shunt to sair device'to maintain the potential difference between the terminals of said device negligible as regards a certain alternating current not of the selected frequency, and a second resonant circuit connected in series with said device whereby currents of selected frequency only may flow therethrough. V

In testimony whereof I have hereunto subscribed my name this 27th day of Oct, 1915.

LEWIS W. OHUBB.

It is hereby certified that in Letters Patent No. 1,333,606, granted March 16, 1920, upon the application of Lewis W. Chubb, of Edgewood Park, Pennsylvania, for an improvement in Signaling Systems for Railways, an error appears in the printedspecification requiring correction as follows: Page 4, line 37, claim 9, and

line 50, claim 10, strike out the words of distribution; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 13th day bf April, A. 1)., 1920.

' M. H. COULSTON,

Acting Commissioner of Patents.

[SEAL 

